This invention relates to ozone generation systems. There are many applications for ozone, including waste and water treatment, disinfection, cleaning, odor removal, extermination, and sterilization. Many ozone generation systems are very large, such as those for municipal waste and water treatment plants, and other ozone generation systems are smaller, such as systems for small industrial and domestic applications. The large ozone generators incorporate controls and features reflecting the significant investment in an industrial plant, while the controls and features of smaller ozone generation systems are limited.
Such smaller ozone generation systems typically comprise a source of feed gas, a device to control the flow of the feed gas with some device or technique to measure the feed gas flow, a plasma cell which generates the ozone from the feed gas, and a device to control the pressure in the plasma cell. The ozone generated is used in an application process. The feed gas may be compressed air, compressed air in which oxygen has been concentrated, or compressed oxygen. The device used to control the flow of the feed gas is normally a manually adjustable valve, and the device used to control the pressure in the plasma cell is an adjustable value at the output of the cell. To monitor the feed gas flow, a rotameter is typically used. The pressure in the cell is monitored by a mechanical gauge.
Unfortunately, in these ozone generation systems the flow and pressure setting are likely to be unstable. The application process pressure is generally quite variable and strongly affects the flow and pressure in the ozone generation system. Rotameters, which are often used for flow measurement due to their low costs, have poor dynamic range, poor resolution, and an undesirable dependency on pressure. Adjustments of the device to control the flow of feed gas and the pressure in the cell device are interdependent, making adjustment an art and not a procedure. These adjustments require the constant attention of a human technician skilled in the operation of that particular ozone generation system. Furthermore, the use of a rotameter and a pressure gauge requires that pneumatic plumbing be coupled to the control panel of the ozone generation system. It is preferable that an electrical control panel remain completely electrical. Additionally, the dependency of flow and cell pressure on the pressure of the application process itself is a major weakness in the system as described above.
A possible solution is to replace the rotameter with a flow controller which is readily available. Flow controllers comprise a flow measurement system, a proportional valve and a feedback system that controls the valve opening to achieve the desired flow control. A flow controller allows the molar flow to remain constant with changes in pressure. But a problem is that conventional flow controllers are expensive compared to a rotameter and a needle valve. Furthermore, a flow controller by itself cannot regulate ozone cell pressure. The ozone cell pressure will vary as a function of flow and as a function of the application process pressure. Therefore, a conventional flow controller is neither an economical solution nor a complete solution.
Therefore, there is a need for an ozone generation system which can accurately and controllably supply ozone to a medium or small scale application processes at a reasonable cost.